Motionless Monday : Spherical shock waves of gun firing

This full-scale Schlieren image shows the discharge of a .44 Magnum revolver.

The basic optical Schlieren system uses light from a single collimated source shining on a target object. Variations in refractive index caused by density gradients in the fluid distort the collimated light beam. This distortion creates a spatial variation in the intensity of the light, which can be visualized directly with a system designed to capture shadows.

Two spherical shock waves are seen, one centered about the gun’s muzzle (the muzzle blast) and a second centered on the cylinder.

Penn State Gas Dynamics Lab seems to have generated this image. Normally I would link to the lab, but it hasn’t been updated in a while. However, You can see some spectacular Schlieren image images taken by Gary Settles of Penn State in the NY Times article: Mysterious Cough, caught on film. Talk Like a Physicist